When should air-entrained concrete be used?
freeze-thaw resistance
The primary use of air-entraining concrete is for freeze-thaw resistance. The air voids provide pressure relief sites during a freeze event, allowing the water inside the concrete to freeze without inducing large internal stresses.
Where can I use air-entrained concrete?
It is beneficial to use air entrained concrete when placing concrete in areas with freeze-thaw conditions. Freeze-thaw conditions occur when the temperature of an environment fluctuates between above freezing temperatures and below freezing temperatures.
What is the main reason concrete is air entrained?
The main reason for using air-entrained concrete is for the increased resistance of concrete against the alternating freezing and thawing cycles of water, which can occur during those periods when the surrounding temperature drops below 0 ° C.
Should air entrained concrete be vibrated?
Don’t Worry About Over Vibrating Air-entrained concrete is produced by adding air-entraining admixtures during batching and the microscopic size bubbles form during mixing. Therefore, workers should vibrate between 5 and 15 seconds to ensure the second phase of consolidation or de-aeration is achieved.
Is quikrete air entrained?
QUIKRETE® Q•Max® Pro Concrete Mix is air entrained for improved freeze-thaw durability and contains a corrosion inhibitor to protect reinforced steel from the effects of chloride and de-icing materials.
Does air entrained concrete crack?
These air bubbles provide a controlled space for water to occupy and permit the expansion of freezing water without creating internal stresses that can eventually cause cracking within the concrete.
How do you air entrained concrete?
HOW AIR ENTRAINING WORKS. Fortunately scientists came up with air entraining technology to beat the effects of the freeze-thaw. During the mixing process, constructors add special agents containing a type of detergent to the paste. They create air bubbles inside the concrete.
Is air entrained concrete weaker?
Air entrained concrete of the same workability and strength was found to have 5% less solid materials hence of lower weight. This will result in an economy of about 5% in the cost of cement and aggregate.
What is the difference between entrained and entrapped air?
When the bubbles are smaller than 0.04 inch, the air is called entrained; larger, and it’s called entrapped. Entrapped air voids are usually irregular in shape while smaller entrained air bubbles are spherical. Air-entraining admixtures stabilize bubbles at a smaller size.
What is air-entrained concrete?
Air-entrained concrete. Air-entrained concrete is ordinary concrete that contains controlled amounts of air in the form of microscopic bubbles. These intentionally entrained air bubbles are extremely small. They range in size from a few thousandths of an inch in diameter to a few hundredths.
How does air entraining reduce concrete slump?
However, air entraining causes the whipped cream effect that reduces the slump by 1-2 inches. Yet the workability stays the same. Thus, air entraining can also be used to reduce the ration of water to cement and therefore increase the strength of the concrete.
How does air entraining technology protect concrete from freezing?
Fortunately scientists came up with air entraining technology to beat the effects of the freeze-thaw. During the mixing process, constructors add special agents containing a type of detergent to the paste. They create air bubbles inside the concrete. Their size can vary from 10 to 500 micrometers in diameter.
How much Air do you put in concretes?
concretes specify 7.5 ± 1.5 percent air for resistance to freezing and thawing; for workability, specify 5.5 ± 1.5 percent for lightweight ag- gregate concretes in the 3000- to 4500-psi (21- to 31-megapascal)